Journal Club on Ureteroscopic Doppler Ultrasonography: Mapping Renal Blood Flow From Within the Collecting System- Evangelos Liatsikos and Roshan Patel

June 28, 2020

Recently published in the Journal of Endourology and the Endourology Society, Jaime Landman, MD, talks with Roshan Patel, MD about his manuscript, titled “Uteroscopic Doppler Ultrasonography, Mapping Renal Blood Flow From Within the Collecting System.” Joined by Dr. Evangelos Liastikos, Dr. Patel notes that while ultrasound has been used in urology since the 1960s, there are limitations to the technology. In collaboration with Vascular Technology Incorporated, Dr. Patel and his team conducted a study on eleven pigs using a 3-French probe, 20 post-Dopper transceiver unit, and Wolf dual-channel flexible ureteroscope to map blood flow within the collecting system at the level of the urothelium.


Evangelos Liatsikos, MD, Ph.D., Assistant Professor of Urology and Head of the Endourology-Laparoscopic Unit at the University of Patras, Greece

Roshan M. Patel, MD, Assistant Professor of Clinical Urology, Director, Kidney Stone Center, UC Irvine

Jaime Landman, MD, Professor and Chairman, UCI Department of Urology, UC Irvine Medical Center

Read the Full Video Transcript

Jaime Landman: Welcome to Endourology Today and UroToday, providing a real sneak peek into accepted manuscripts via a very exclusive collaboration with the Journal of Endourology and the Endourology Society. We will literally be looking at manuscripts that are accepted for the Journal of Endourology prior to their publication, even online. We're going to select some of the most exciting manuscripts, which is exactly what we've done today. And today we'll be talking to Dr. Roshan Patel from the University of California Irvine who had a recent manuscript accepted. Welcome, Dr. Patel.

Roshan Patel: Great. Thank you so much for having me, Dr. Landman.

Jaime Landman: It's a pleasure. Now, because your manuscript has to do with blood flow and puncture, I also invited a very distinguished endourologist and a very close friend of mine, Evangelos Liatsikos, from Greece, who will also be commenting on your manuscript and I do think there may be some interesting dialogue because of different opinions. Welcome, Evangelos.

Evangelos Liatsikos: Thank you very much. Nice to join you.

Jaime Landman: Well thanks for coming. In this era of COVID, which is so challenging, we can still do global collaborations and this is a great way for us to stay socially isolated and yet get some real productive work done. Roshan, tell us about your manuscript that's going to be published. What's it titled? What did you do?

Roshan Patel: Sure. Thank you so much again. As to the title of the manuscript, is called "Uteroscopic Doppler Ultrasonography, Mapping Renal Blood Flow From Within the Collecting System". And so ultrasound has been used in urology since the 1960s and it's a beautiful way of minimally invasively recording and evaluating blood flow. Some of the limitations with ultrasound probes as they're currently out there is that it's only used to map the surface of the kidney and it's got to be put on top of the patient or on top of the renal capsule. And so what we did is we collaborated with a company called Vascular Technology Incorporated. And what they did was, they have a lot of probes that they use for different modalities such as in robotic prostatectomies, and also in other surgeries like that. And what they did for us was they made a 3-French probe that was about 120 centimeters long and they coupled it to a 20 post Doppler transceiver unit. And that allowed us to put that within a flexible ureteroscope.

Now one of the nice things about this, was that when using a traditional ureteroscope, it has a single channel and if you're using a 3-French probe through a single channel, the irrigation is completely limited. And so what we did in this study was we used a Wolf dual-channel flexible ureteroscope, which allowed us to use one of the channels for the Doppler probe while using the second channel to provide irrigation. We could very accurately move the ureteroscope within a pig kidney. Specifically with this study, what we did was we used 11 Yorkshire pigs and it was a non-survival study. And what we did was we used this novel Doppler probe, and using a flexible ureteroscope with the assistance of fluoroscopy, we went in throughout each calyx in the upper, inner and lower polar regions and also in the infundibula, and essentially mapped out the flow from within the collecting system at the level of the urothelium.

This has never been done before and while there's been a lot of studies, especially looking at cadaveric kidneys with Dr. Sampaio's seminal work many years ago, and also other CT studies that have been done looking at the vasculature, it's never been at the urothelium level. And the thought was if we can find out where the blood flow was at the most, at the level of the urothelium, it could aid in providing safe puncture during percutaneous nephrolithotomy. That was the general outline of the study. And I can go into and discuss further the results, as we move along in this conversation.

Jaime Landman: Just so I can understand. The thing that made this possible and unique is that you have this unique scope that allows you to have basically a 3-French Doppler and still be able to maneuver the kidney really nicely and see what you're doing really nicely. And this unique study probe, which I don't think is clinically available, right?

Roshan Patel: That's correct. It's not FDA approved. It was made specifically for us as we had the idea of being able to do something from within the kidney rather than from outside of the kidney.

Jaime Landman: Terrific. Really the findings are what were quite extraordinary and you made beautiful studies. Could you just give us kind of a quick recap of the results and maybe why this is clinically relevant?

Roshan Patel: Sure. And so what we found as we moved this Doppler probe around the pig kidney, was that inevitably at the center of the papilla, there was no flow detected whatsoever in all 11 pigs that we studied. Now moving along the fornix, interestingly, we found more blood flow or higher blood flow at the 6:00 o'clock position and then looked at collectively as compared to the fornix and the papilla as compared to the infundibula. The infundibula invariably had much higher blood flow than anywhere else. And what we did, and I didn't mention this in the methods, not only did we use a Doppler to detect the flow, we also used a Holmium laser fiber and punctured the urothelium and measured bleeding times, too. And bleeding times correlated with the amount of auditory flow that we're hearing on the Doppler device. Again, the conclusions of the study were the fornix has less blood flow than the infundibula and invariably the middle, or the papilla, the center of the calyx, had no blood flow whatsoever and would seem to be the safest location to perform a puncture when doing a percutaneous nephrolithotomy.

Jaime Landman: Right. The study seems valuable in that as you said, the anatomy of the pig is very similar to that of the human. And that was Bagetti Filho who published that and they followed up the work of Sampaio who also showed it. I'm going to ask you some obvious questions because this has to do with puncture of the kidney largely for percutaneous nephrolithotomy. Was there any difference between upper pole, interpolar and lower pole calyces with regards to blood flow? Because that's obviously different places where we sometimes puncture the kidney.

Roshan Patel: Yeah. In our study, there's no statistical difference in either the upper, inner, lower pole. And also interestingly, there's no difference between the anterior and posterior calyces.

Jaime Landman: Now you beat me to the punch because obviously there's tremendous clinical debate as to whether a supine or prone approach to PCNL is better. And there are strong arguments both ways. In terms of blood flow, no difference.

Roshan Patel: That's right. And I think the difference here, and as you mentioned, at the level of the urothelium, there is no evidence of increased blood flow. When you're going through an anterior calyx, obviously the concern is that you're transversing more of the renal parenchyma when you're performing the surgery. But at least at the level of the urothelium, there was no difference.

Jaime Landman: Okay, so the question I would ask then is if you want to technically not puncture the infundibulum, that requires a fair bit of precision. Do you think there's any advantage, then, to the endoscopic approach that Clayman and Boren initially introduced to PCNL?

Roshan Patel: Yeah, I think the best analogy that I have is that you can either do a puncture with your eyes closed in trying to do something thoracoscopically or via ultrasound. Using endoscopic guidance where you're actually seeing where the needle is coming in, once you're doing it that way, I don't think there's any way to increase precision. At least in terms of knowing exactly where your tract is. Otherwise, you're just looking at it with your eyes half-open and half-closed.

Jaime Landman: All right, so really Roshan, you sound pretty definitive. You like endoscopic, you like a calyceal puncture, you're very anti-forniceal puncture on this and your data is this Doppler stuff, the sticking of the kidney and you're going to back it up with the anatomy studies. Now Evangelos, the reason I invited you to join us is not only because you're an extraordinary expert in endourology, but because in 2017 I remember you had an abstract where you prospectively randomized people to either an infundibular poke or a calyceal poke and you showed no difference. I appreciate you reviewing this article before anyone else has had a chance to see it. What are your thoughts?

Evangelos Liatsikos: Now, let me identify a couple of points. First of all, we are talking about papillary and non-papillary punctures. Forget the infundibulum concept because what is an infundibulum? There are kidneys that have a very narrow infundibulum. Other kidneys that have very wide infundibulum, small, short, large. It's either papillar or no papillar. That's how we are dealing with this concept. Now this study that I used is an excellent concept of this Doppler evaluation. Two things, the blood flow is evaluated at a urothelial level. I would expect that there is no urothelial blood supply at the papillar level. Now, if we want to clinically address the relevance of it though, where do we get the bleeding from when we puncture? Do we get it from the urothelial level? Or do we get it from major vessels that are fairly deep inside, further than one side from what we were evaluating right now?

And you know, if the papilla would be an avascular plane completely, then how do we justify this one to 2.6% of emboli that we see now papillary puncture, you know that the avascular plane of broad L should be either avascular or it's not avascular. You can't have transfusion rates of three or four or five percent on papillary punctures. So that's how this whole thing started in our mind. This paper really makes it ... I like it because it's the first time I'm reading something on evaluating the blood vessels from the inside out, which is important. It would be interesting to be able to depict a bit more depth to have a bit more depth than one centimeter to be able to get, let's say two or three centimeters of depth in the area where the Doppler would go.

That would clearly give you a lot more definitions of what it means to have a risk and not a theoretical risk of bleeding. As you know, we always read in the books there is always a theoretical point of bleeding in our books. I would just add something. If we combine in the future, I would love the idea of having the Doppler coming retrograde and then the electromagnetic puncture coming antegrade and having a needle with a Doppler or something like this. Then when you'd really go to an avascular plane, and it would be interesting to see where that plane would be, because for me it's not a given it's the papilla. It could be anywhere else around the kidney. If you can identify where the big vessels are and you avoid them, there's no bleeding there. At least that's how we see it in our department.

Jaime Landman: Thank you for that comment and I really appreciate it. It's interesting, you are correct. When you look at your 2017 abstract at the title is "Papillary Versus Non-papillary Puncture". But I do have to admit that when I look at the materials and methods, you had two groups, either papillary, which was group one or infundibular renal access, which was group two. So from the perspective of the world, you brought this. It was a very unique concept that we've been debating and we debate at UCI a whole lot. But you have to be careful because your manuscript specifically says in the materials and methods.

Evangelos Liatsikos: No, I know, but Jaime, you need to keep in mind that anatomies of all kidneys are all different. So the typical infundibulum that we see in the Sampaio work is not what we see in our everyday practice. So it's papillar and then yes, infundibulum if you want. But in reality, it goes through the infundibulum to the pelvis through parenchyma. That's a real puncture. That's what it means by saying we don't go through a small infundibulum anterior, we go to the best location for us, for the wire to go down the ureter and then to be able to navigate within the kidney. So that's the non-papillary puncture.

Jaime Landman: Right. Well, I'll be honest, we're very particular about the infundibulum because I've seen a couple of infundibular stenoses. So we definitely try and puncture at the papilla as best we can and then not dilate the sheaths through the infundibulum. I'm going to turn this to Roshan. One of Evangelos' biggest criticisms was that this isn't deep enough. You only go one centimeter in. Roshan, what's your thought about the depth of penetration of your Doppler in the vascular supply?

Roshan Patel: I thought a couple of very important points were made here and I think a combined approach where you have a Doppler that's one centimeter or the depth was even further combined with an electromagnetic approach is the best way to thinking about it. I thought that's a great point. And then the second thing that I thought is extremely valuable is that I completely agree. Everybody's different, everyone's anatomy is different and I think that is a testament to the value of this. If we could on a routine basis, map out where we're going to puncture in real-time in each patient, we would then be able to find the best area to puncture.

And then if we could combine it where we could accurately then dilate that track, I think that would lead to the least morbid approach to PCNL. My favorite kind of analogy for this is that we are able to land rovers and satellites in outer space. We get pictures from Pluto, yet we can't reliably put a needle through the kidney and dilate a tract accurately, and we're talking about 10 to 15 centimeters as a distance. So maybe the approach either is inside out to do the puncture or just their combined approach from inside to outside such that we can then do this in a more precise fashion.

Jaime Landman: Evangelos, any final comments?

Evangelos Liatsikos: Oh, I think we are concurring on our final comments. I think that it's not the papillary puncture. It is depicting where would be the less morbid approach to the kidney, because it's not a given that the papilla is the less morbid approach. It could be with a 3D construction on the vessels and with a Doppler combined with electromagnetic, there could be another point inside the kidney that is less morbid than the papilla, than a particular atomical, very small and very narrow papilla. So I think that the technology will give us a lot of information in the very near future and we will make our [inaudible] access much less morbid.

Jaime Landman: Well, thank you again, Evangelos. I have to thank UroToday, as always, for allowing us a venue to provide the most updated and real-time information. Doctor Roshan Patel, thank you for this wonderful manuscript. Dr. Evangelos Liatsikos, as always, thank you for your wonderful commentary, and I really appreciate everybody. Finally, that's the end of our inaugural episode of Endourology Today. Again, thanks to the Journal of Endourology, there'll be a link to Dr. Patel's manuscript as well as thanks to the Endourology Society for making this possible.